The present invention relates generally to an image sensor and relates more particularly to a crosstalk-proof image sensor.
Image sensors comprising photosensitive semiconductor devices are suitable for constructing compact type facsimile machines, copying machines, image scanners and the like. An example of such prior art image sensors is illustrated in FIGS. 1(A) to 1(C) for fasilitating the understanding of the background of the present invention. The image sensor is a line sensor which is provided with a row of photosensitive regions. FIG. 1(A) is a plan view of an electrode arrangement. A number of electrode strips are formed in parallel together with head portions 1 located just above the underlying photosensitive regions. Each head portion is connected with a driving IC through a lead portion 2 and a contact 4 by means of wiring 3.
FIG. 1(B) is an expanded view of the head portions of the electrode arrangement and FIG. 1(C) is a cross sectional view taken along a--a line of FIG. 1(B). The photosensitive region is comprised of a transparent common electrode 6 formed just on a glass substrate 5, a photosensitive semiconductor layer consisting of a p-layer 8, an i-layer 9 and an n-layer 10 and an opposed electrode layer 7 stacked in this order. The photosensitive semiconductor layer and the opposed electrode layer are divided into a row of photosensitive regions by grooves 11. The groove is provided for avoiding current leakage between adjacent photosensitive regions.
The grooves 11 are formed by etching after deposition of the respective layers. During the etching process, however, the photosensitive regions are often damaged. The grooves 11 may receive some debris which may form bypass current paths between the layers. The formation of this grooves 11 is indispensable in order to avoid crosstalk between pixels because the ratio of the resistance of the layer 10 in a lateral direction to the resistance in the direction normal to the layered structure is only 10 or lower. The ratio can be increased by making use of amorphous silicon semiconductor to some extent. However, the ratio is not so low as to dispense with the formation of the grooves.